Protection of structures, such as roofs and walls, through the use of panels constructed of protective materials, such as asphalt, slate or metal, is well known in the art. For example, U.S. Pat. No. 2,873,699 describes a metal roof protection structure, including a plurality of side-by-side interlocking roofing panels. Side-by-side locking panels produce a vertical pattern on a finished roof. Each panel is affixed to the underlying roof structure by driving a nail through the panel into a roof board. A next adjacent panel is positioned relative to the affixed panel, such that the nail head is covered and moisture is inhibited from seeping through the hole created by the nail and does not wet the underlying roof board. This panel joint structure does not completely inhibit water access to the nail head, however, because the panels fit snugly together (i.e., exhibit a "glove fit"), and capillary action produces movement of water between the panels to the region of the nail head.
Capillary and siphoning action has been recognized as a problem in the roofing industry. U.S. Pat. No. 4,878,331 describes a solution of this problem for the production of vertical roof patterns. This patent discusses vertical roofing panels having two interlocking ridges disposed on opposed longitudinal edges of the panel. One ridge is smaller than the other, and, when two such panels are interlocked, a space of sufficient size to disrupt capillary action is located between the top walls and/or between one set of side walls of the ridges of the two panels.
Also, the rigid attachment site of the panel design of U.S. Pat. No. 2,873,699 does not accommodate normal expansion and contraction of roofing panels in response to changing environmental temperatures. As a result, rigidly affixed panels are susceptible to buckling, cracking, deforming, and shearing of fastener heads.
Moreover, panels designed to produce horizontal patterns have encountered many problems not present or present to a lesser or different extent in installation of panel assemblies exhibiting vertical patterns. For example, horizontal patterns are subjected to different wind uplift conditions than are vertical patterns. Also, the process of installing roofing panels generating a horizontal roof pattern gives rise to greater concern regarding available roof work space than does installation of vertical roof patterning panels. The few roofing panels in existence designed to produce horizontal patterns require installation to occur from the bottom of the roof upward. This configuration necessitates that the roofer stand and work on some previously affixed panels to install other, higher roofing panels. The roofer's weight and work activity relative to affixed panels may damage those panels by bending or denting the panels or by scratching the panel finish.
U.S. Pat. Nos. 3,363,380 and 4,803,818 appear to discuss roofing panels designed to produce horizontal roof patterns. The first patent is directed to shingles. As discussed above with respect to panels designed to produce vertical roof patterns, capillary action is a recognized problem in the roofing industry. The shingles of this patent are joined in a glove fit manner at the portion of the shingle joint adjacent the underlying roof boards at the downhill end of each shingle. This partial glove fit shingle joint structure will permit water to seep into the joints therebetween by capillary action. Like other commercially available horizontal roofing panels, the panel of the second patent is not self-interlocking in that a locking member in addition to the panels themselves is required to lock the panels together. This additional component adds to the complexity and difficulty of the roofing process.
U.S. Pat. No. 4,356,673 is directed to siding panels that generate a horizontal pattern upon installation of a plurality of such panels. The patented siding panels are not self-interlocking, however. Consequently, the siding process is made more complex by the requirement of an additional component to lock the siding panels together.